Electronic display systems are commonly used to display information from computers. Typical display systems range in size from small displays used in mobile devices to very large displays visible to thousands of viewers. Large displays are sometimes created from tiling smaller display devices together. For example, video walls using multiple video displays are frequently seen in the electronic media and flat-panel displays are tiled to create larger displays. Multiple projector systems used to create a large, tiled, high-resolution display are also available.
Tiled displays are well known in the prior art. For example, U.S. Pat. No. 6,683,665B1 issued Jan. 27, 2004 describes tile structures wherein each tile has a display portion and an electronics portion. The tiles are fastened together into an array with the use of a frame. Alternatively, U.S. Pat. No. 6,498,592 issued Dec. 24, 2004 describes the use of a single substrate with electrical devices and a display. However, as disclosed, these designs require the use of vias through the substrates and are problematic for displays requiring a hermetic seal for the display components, for example in an OLED display. Vias in glass substrates are difficult to construct and the use of alternative substrates are not well suited to sealing the display materials. Moreover, the design requires an additional frame and is not well suited to roll-to-roll manufacturing.
Another technique that relies on overlapping the display tiles is described in WO 03/042966 entitled “Display for a Large Panel Display Consisting of Tiled Displays”. The method disclosed uses a complex support structure and a plurality of printed circuit boards. Moreover, tile seams may be visible when the display is viewed off angle.
A display may be formed on a single substrate but utilize a tiled control structure. Display elements are formed in a regular pattern across the substrate. Since each display element requires two electrodes to provide current to the display element, each display element has two electrical connections to the element. In order to conserve space on the substrate, these connections are shared wherever possible. A conventional, prior-art passive-matrix connection scheme forms a horizontal array of electrodes in one dimension and a vertical array of electrodes in a second dimension. The display elements are formed where the horizontal and vertical electrodes overlap with the light-emitting or light-controlling elements formed between the electrodes.
Using this connection scheme, only one row or column of display elements can be illuminated at once. This limitation requires that the display elements be refreshed frequently and, consequently, driven at a high frequency and with high current. The driving requirements, in turn, limit the size of the display, since electrodes that are too long or refresh frequencies that are too high, require expensive driver circuits.
A simple, well-known approach to dealing with this limitation is to divide the display elements on a single substrate into four groups, each group having its own electrode connections. For example, referring to FIG. 10, a tiled, passive-matrix, flat-panel display is formed on a single substrate 12 and divided into four groups 50, each group having a set of control signals 52. In this fashion, a larger display element matrix can be formed. However, this approach is limited to four groups and also requires the use of connections on all four sides of the substrate 12 rather than only two sides.
There is a need therefore for an improved tiled display system that overcomes the problems noted above.